1. Field of the Invention
This invention relates to a coating composition for inhibiting corrosion of metals, and in particular, to a water-base coating composition that forms a readily strippable film on metal surfaces.
2. Brief Statement of the Prior Art
Various materials and methods have been used in attempts to provide a temporary corrosion protective coating for metal surfaces. In my prior patent, U.S. Pat. No. 4,584,175, I disclose preparation of plastic film which contains varioius corrosion inhibitors and which is effective in preventing corrosion of metal objects that are wrapped in the film. Many objects, however, are not readily wrapped in plastic film, and a need exists for a temporary coating which can be sprayed or otherwise applied to metal objects, and which can be readily stripped from the object once it has been removed from a corrosive environment. Film formers containing lead and zinc chromates and various polyacrylates have been used to coat metal objects. One of the difficulties with the polyacrylates and other film formers used heretofore has been that they are not readily strippable and, instead, must be dissolved from the surface of the metal. They are commonly removed by washing with an aqueous detergent or a weak aqueous solution of ammonia. In many instances, these coatings cannot be used because washing the coatings from the metal object is more damaging to the metal surfaces than the corrosion sought to be prevented. Thus metal surfaces having aluminum or zinc surfaces cannot be readily washed with most aqueous detergents.
Most film formers do not form readily strippable films which are impervious to gases such as oxygen and water vapor. Additionally, most strippable coatings do not adequately protect against scratches and other mars to the surface of the metal. The lack of toughness and film strength essentially precludes most film forming resins as suitable corrosion protective coatings.